Manufacture of seamless tubing



Nov. 16 1926.

P. OTTO MANUFACTURE OF SEAMLESS TUBING Filed August 51 1925 3 sheets -sheet l INVENTOR verting the hollow bod Patented Nov. 16. 1 926.,

UNITED STATES 1 1,607,475 PATENT OFFICE.

PETER OTTO, OI DUSSELDORF, GERMANY, ASSIGNOR TO THE YOUNGSTOWN SHEET AND TUBE COMPANY, OF YOUNGSTOWN, OHIO, A. CORPORATION OF OHIO. h

mmurncruan or sammss roams.

Application filed August 81, 1925, Serial 1T0. 53,547, and in Germany July 8,

Seamless tubes have heretofore been produced by first formin a hollow body by means of a piercing mi 1 into the desired tube. The exceedingly hlgh straining of the material in the rolling from the solid into the hollow cross sect-ion causes the finished tube to show laminations and chips, which should not occur if higher requirements are asked of the tubes as regards tensile strength, uniformity and exactness, as in that case there would be a relatively large waste of material, labor andtime and also a rela tively large consumption of power.

The method of forming a hole in the work piece by means of a mandrel is also obj ection-- able when the tube is required to meet certain rigid conditions; This is because the material is subjected to such a large amount of work during the tube formation and because certain portions of the blank are necessarily displaced in a considerable amount. The piercing process therefore has the disadvantage that unless the operation is held within favorable limits the tubes is damaged.

Casting the original ingot. hollow in a sand mold has also been found very unsatisfactory as it leads to irregularities. Each ingot could not be cast separate as the waste due to discarding of the heads was much too large. If ingots of suflicient-length to be cut up into a number of work pieces were cast, the structure thereof varied ac- ;cording as to whether the separate work pieces were taken from the lower part of the casting or more towards the top where the blow hole is situated. It was impossible to cast the tubular ingots in a horizontal position by reason of the non-uniformity of the material as regards compactness and purity in the various layers throughout the section.

, Moreover, there was always the danger that the tubular ingots would contain inclosures of molding sand, especially on their inside I wall, which could not be detected, but which would render the rolled tubes unfit for the best service.

- I have discovered that all of the above objectionable features of the methods heretofore employed are overcome by producing the initial hollow work piece by the method of centrifugal casting. By centrifugal casting, a tubular ingot can be cast horizontally or substantially horizontally, which is .of substantially the same uniformity along its and thereafter con-' specifically heavier metal outwards and the lighter slag is forced towards the interior. T ere is nothing to prevent constructing the initial ingot of such diameter that the further treatment thereof can be effected without the considerable strainin of the material as in the case of the 'ot er proc-' esses above referred to. K The use of the centrifugal casting process for. making the hollow initial work piece for the rolling of seamless tubes therefore shows advantages hitherto not thought of, which are made manifest not onl by the cheapness of manufacture in itsel but also by the avoidance of waste. Another advantage of this novel proce which is of great importance is due to the fact that the casting heat contained within the hollow work piece can be utilized direct. This was hitherto not possible with the cast ing in sand molds. In the centrifugal casting process,however, the conditions are quite different, as in the centrifugal casting pgocess the casting'obtained is ready at once for the rolling steps, without further treatment, whereas in the process of casting in sand molds it is necessary to cut off the discarded heads, casting funnels and the like before the hollow bodies can be conveyed to the rolling devices. .By reason of the necessity of subjecting the hollow work pieces obtain ed by other casting methods to an after treatment and to a thorough control, before they can be conveyed to the rolling devices,

'a utilization of the casting heat is out of the question. It will be apparent, however,

that this can be done very well in the new process, as the hollow body obtained by casting represents a purel tubular form without any projection, and as slag formation on 'the inside will be removed automatically-in J. I work should occur and it also may be utilized for heating the hollow bodyumformly throughout. or for mparting thereto a different temperature or chemicahor physical properties other than .those which it obtains from the casting process, particularly with regard to the required various tensile strengths of the tubes to be producgd. It alsomay be necessary for the rolling process to be carried out at a considerably lower temperature than that possessed b the hollow body when it leaves the mol It would be necessary to cool the hollow body either by allowing it to rema'1n for some time exposed to the air, before at 1s subjected to the rolling process, or it com d be cooledartificially.

According to the present invention therefore the centrifugal casting process is used only for the production of comparatively short hollow initial'ingots which are further treated by a rolling process until a tube of the required dimensions s obtained. In its simplest form, the invent on contemplates passing the hollow ingot directly, from the casting mold into the IOlllIlgJIllll. 7

Suitable apparatus-for carrying out the process is shown in the accompanymg draw:

- mill.

Referring to the construction shown in Figure 1, the casting device comprises a mold "2 closed'at its lower. end by a cover 3 to such an extent that the material which introduced into the mold cannot flow out. The mold is rotatably mounted in bearings 4 and is adapted to be rotated by gears 5 and 6. At the inletside of the mold is provided a casting truck 7' which receives the molten metal from the casting ladle 8., At the other side of the mold there may be provided any suitable form of conveying device for conveying the cast body 9 to a rolling mill. This conveying device may carry the hollow body into a chamber of the character referred to above for the purpose of regulating the temperature of the cast ingot as explained.

The casting of the hollow body is effected in such a manner that the molten metal supplied to the rotating mold is uniformly distributed over the required length of the mold. by suitably moving the casting truck 7 so that a hollow body having walls of substantial uniform thickness is obtained. After tie casting has been completed the cover 3 isremovedso that on further rotation'of themold the hollow body slides out of it and is received by the conveying device referred to.

Fi re '2 shows'casting apparatus very uniformly distributed in the mold chamber I I to produce a hollow body having walls of substantially uniform thickness;

After thehollow ingot 9 has been obtained in the manner described, it may be passed toa roughing mill consisting of a pair of grooved rolls 18 and a mandrel 19, such as shown in .1 igure 3 or it may be passed to a roughing mill of the Mannesman type, such as shown in Figure 4, consisting of the pair of rolls 20 and the mandrel 21. In this preliminary rolling in the roughing mill, the hollow ingot obtained by the centrifugal casting may be only compressed to such an extent as to smooth the walls of the same and to remove the slag or this preliminary rolling process can be used for the purpose of obtaining such variations of diameter as are desirable for carrying out a smooth finishing rolling operation.

a The finishing rolling operation is preferably carried out in a pilger mill which is shown in- Figure 5- This mill comprises a pair of pilger rolls 22. Each of these rolls has a groove 23 extending part way around the same, the rolls being cut away between the ends of the grooves, as indicated by the reference numeral 24. The hollow ingot 25 received from the roughing mill is supported on a mandrel 26 and the ingot and mandrelare yieldingly forced in the direction of the arrow 27 between the rolls by fluid pressure means (not shown) The rolls rotate in-the direction of the ar ows 28, and thereby tend to force the ingo and mandrel backwardly in a direction counter to the direction in which they are. moved by the fluid pressure means. The rolls are shown with their grooved portions biting into an unreduced portion of the ingot. As

the rolls continue to rotate this unreduced portion is rolled down to the thin' wall of the tube-and when the cut away portions 24 come opposite each other another unreduced portion of the ingot-is moved between the tions in the same manner.

While I have shown and described certain preferred forms of apparatus for carrolls to be acted upon by the grooved por rying out my new process, it willbe understood that the invention is not limited to the particular devices shown. For example the finishing rolling may be done by an auto- 1. In the manufacture of seamless rolled tubes, the steps consisting in forming an initial hollow ingot by centrifugal casting and thereafter rolling the ingot so formed into the desired seamless tube while utilizing the casting heat contained within the ho low ingot in the rolling, substantially as described. y

2. In the manufacture of seamless rolled tubes, the steps consisting in roducing an initial hollow ingot by centri ugal casting, passing. the ingot so produced through a chamber wherein the ingot is brought to the desired temperature condition, andthereafter rolling the ingot into the desired. tube, substantially as described.

-3. In the manufacture of seamless tubes, the steps consisting in forming-an initial body by centrifugal casting, the body being in the form of an uninterrupted ring at any cross-section thereof, and passing the body in such form lengthwise through a tube mill in the ordinary manner to pro-,

duce a seamless tube, substantially as described.

4. In the manufacture of seamless tubes, the steps consisting in forming an initial body by centrifugal casting, the body being in the form of an uninterrupted ring at any cross-section thereof, and, before the body has become cold, passing it in such form lengthwise through a tube mill in the ordinarymanner to roduce a seamless tube, substantially as described- 5. In the manufacture of seamless tubes, the steps consisting in forming an initial body by centrifugal casting, artificially varying the temperature of the blank thus produced from the temperature which it possesses due to the casting step, the body being in the form of an uninterrupted ring at any cross-section thereof, and passing the body in such form lengthwise through a tube mill in the ordinary manner to produce a seamless tube, substantially as described.

6. In the manufacture of seamless tubes, the steps consisting in introducing molten metal to an elongated centrifugal mold so as to cast a hollow body, shifting the point of introduction of the molten metal during the casting operation, the cast hollow body thus produced being in the form of an uninterrupted ring at any cross-section thereof, and passing the body in such form lengthwise through a tube mill in the ordinary manner to produce a seamless tube, substantially as described.

In testimony whereof I have hereunto set my hand.

PETER o'r'ro. 

